This invention relates, in general, to semiconductor diodes, and more particularly, to a semiconductor diode having a controlled voltage drop.
Semiconductor diodes are commonly made from a P-N junction. In other words, the diode is formed from a P-type conductivity material in contact with an N-type conductivity material. It is also common to form a diode from junctions used to make a transistor. In such a case the collector and base electrodes of the transistor are shorted together to form the anode of the diode while the emitter electrode forms the cathode of the diode. In some cases diodes have been formed from a transistor structure having one emitter electrode, two base electrodes, and two collector electrodes. The two base electrodes and the two collector electrodes are all shorted together in order to form the anode contact while the emitter electrode is used as a cathode contact. All of these diode configurations have essentially the same voltage drop from anode to cathode. Varying the physical size of the collector or base areas does not have an appreciable effect upon the voltage drop of the diode. By reducing the physical size of the emitter by one half, the voltage drop can be made to increase by approximately 20 mv. The other known method of increasing the voltage drop across a diode is to increase the current flowing through the diode. Doubling the current flow through the diode increases the voltage drop by approximately 20 mv. In many applications it is desirable to increase the voltage drop without increasing the current flow. To obtain an appreciable voltage drop a resistor can be added in series with a diode; however, this consumes additional silicon area.
Accordingly, it is an object of the present invention to provide a controlled voltage drop diode.
Another object of the present invention is to provide a diode having an increased voltage drop without requiring additional silicon area or increased current flow.
Yet a further object of the present invention is to provide an increased forward diode voltage drop by using an extra electrically floating collector-base short to provide a voltage divider effect on the active base.